[OpenLayers-Users] ModifyControl Select/Delete Vertex?

[Alexandre Dubé]

Hi Rob,

   This would indeed be a nice feature to have.  Looking at the 
ModifyFeature control, I think this could be easily accomplished with 
minor modifications.

   If we look at the ModifyFeature control, it creates a DragFeature 
control to allow dragging the vertices around.  When you "mouse hover" a 
vertex feature, a callback function is triggered because it was defined 
here :
https://github.com/openlayers/openlayers/blob/master/lib/OpenLayers/Control/ModifyFeature.js#L267

   That's the callbacks for the OpenLayers.Handler.Feature object the 
drag control needs to interact with features on the map.  The drag 
control defines its callbacks method in the featureCallbacks object :
https://github.com/openlayers/openlayers/blob/master/lib/OpenLayers/Control/DragFeature.js#L119

   and here's the list of callbacks you can set to a feature handler: 
click, clickout, over, out, and dblclick.
https://github.com/openlayers/openlayers/blob/master/lib/OpenLayers/Handler/Feature.js#L30

   So, back in the ModifyFeature control, you could add a 'click' 
callback function just next to the 'over' one.  Instead of coding what 
you want it to do directly in the source, just define an abstract 
function that needs to be overriden OR you could fire an new vector 
layer event : vertexselected (which would need to be added to 
OpenLayer.Layer.Vector).

   Whoa, sorry for the long reply :)   In short, try to create a 
delegate method or event we could register to to do whatever we wanted 
on vertex selection.

   Does that make sense ?

HTH,

Alexandre


On 13-02-26 11:42 AM, Robert Smart wrote:
> Hi All,
>
> I'm trying to port some existing functionality into open layers and have
> managed to get most of it working. I'm just stuck on a seemingly simple
> task.
>
> The current code allows a user to highlight a polygon vertex by 
> clicking on
> it (which changes its colour), so that the user can then press a delete
> button to remove the vertex.
>
> Using the modify control I'm able to display the vertices, and even 
> delete
> them if I click on it and then press 'del' on my keyboard, but this is 
> not a
> great solution as there is no visual clue as to what vertex has been
> selected.
>
> So is there a way to highlight or change the colour of a single vertex 
> the
> user has clicked on? is there then a way to remove that vertex via 
> code and
> have the polygon redraw on the screen to suit?
>
> I think this would actually be quite useful as a standard feature as 
> there
> are many cases where one might want to select an individual vertex.
>
> Thanks,
>
> Rob
>
>
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-- 
Alexandre Dubé
Mapgears
www.mapgears.com

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